"How much time do I have?" is the first question many speakers ask when getting invited to speak at an event. It is an important question: a 5 minute presentation is dramatically different from a 20 minute one. Beyond 20 minutes though, it does not make that much of a difference. These presentations are "long". I very much doubt that you will do a better job in convincing your audience in 60 minutes than in 20. In fact the opposite might be true.
If you get offered a 60 minute slot, ask yourself whether you really need it, or you should cut it to 20-30 minutes instead.
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